This invention relates to a propeller damping arrangement for marine propulsion devices and more particularly to an improved coupling and cushion for drivingly connecting a propeller to a driving shaft.
In most forms of marine propulsion, a propeller is utilized for driving a watercraft through the water. The blades of the propeller and their cooperation with the water, however, tend to cause vibrations which can be both objectionable to the occupants of the boat and may, in extreme cases, damage the running components. It has, therefore, been the practice to provide a flexible coupling between the propeller and its driving shaft which normally comprises an elastomeric sleeve through which the driving forces are transmitted. Although theoretically such an arrangement may provide adequate vibration damping, in practice these devices cannot provide sufficient resilience. In view of the fact that the driving forces must be transmitted through the elastomeric sleeve, it is necessary to use, with prior art constructions a relatively rigid sleeve so as to transmit these driving forces. As a result, the sleeves with the prior art constructions are too rigid to effectively dampen the normal running vibrations.
It is, therefore, a principal object of this invention to provide an improved vibration damping coupling for a marine drive.
It is another object of this invention to provide a marine drive coupling that is effective to absorb normal vibrations and yet which has sufficient rigidity to transmit driving forces.
Most marine drives employ a forward, neutral, reverse tranmission so that the boat or associated watercraft may be driven either in a forward or rearward direction. The driving forces transmitted in the forward direction are always considerably greater than those in reverse. However, the couplings heretofore employed have provided the same degree of vibration resistance in both directions.
It is, therefore, a still further object of this invention to provide a coupling arrangement for a marine drive that offers more resilience in the reverse mode than in the forward mode.